1. Field of the Invention
The present invention relates to processors of photosensitive material. In particular, the present invention is an improved system for transporting photosensitive webs through processing tanks of a processor.
2. Description of the Prior Art
A wide variety of processors have been developed to process webs of photosensitive materials. These processors typically include a plurality of tanks containing photoprocessing solutions, and a dryer. The web of photosensitive material is transported through the tanks and through the dryer by a transport system which typically includes a plurality of driven rollers.
Some types of processors are required to accept webs of various widths. An example is a graphic arts processor for processing resin-coated phototype-setting paper webs. These webs can vary in width from, for example, 35 mm to 203 mm (8 inches) and may be supplied from a roll or from a light-tight cassette. The length of the phototypesetting paper webs can range from 7 inches to several hundred feet in length. This presents several difficult problems with respect to the transport system of the processor. First, in a processor adapted to be used with a wide variety of different widths of webs, it is desirable not to have to change the entire transport system each time a different width web is processed. As a result, it is impractical to provide guides within the tanks and the dryer. Thus the transport system permit the web to track reliably through the processor with guiding only at the inlet end of the processor.
Second, with long length webs, there is significant danger of damage, particularly in the event of slight angular misalignment of the web at the inlet end. In conventional transport systems, any wandering of the web can result in wrinkling or damage to the edge of the paper.
Third, in conventional transport systems the speed of the various rollers of the transport system must be closely synchronized to prevent damage or even breaking of the web as a result of stretching. Similarly, damage can occur to the web in conventional transport systems if the later rollers are operating at lower speeds than the earlier rollers, since the web may buckle or wrinkle and can, in some instances, even jam the transport.
U.S. Pat. No. 3,830,419 by Conrad E. Lee, which is assigned to the assignee of the present application, describes a transport system for photographic processors which uses tapered rollers. The transport mechanism includes a plurality of pairs of oppositely tapered rollers having opposed surfaces which are spaced apart a distance which is slightly greater than the thickness of the web. The pairs of tapered rollers are arranged so that the web is driven only on the marginal edge portions of the web. This minimizes damage to the images which are typically contained in the central portions of the web.